rpm and the power band

[badkuk]

pardon the rather naive question: usually, gas engines have maximum hp/torque at 5000-6000rpm, right? regardles of whether gas or diesel, why bother designing the engine to run up 7000, maybe even 11,000rpm, when the max hp/torque is around half of that? wouldn't all that revving beyond that point be, um, pointless?

[the_wildthing]

Because it stays around that range.

[Jun aka Pekto]

pardon the rather naive question: usually, gas engines have maximum hp/torque at 5000-6000rpm, right? regardles of whether gas or diesel, why bother designing the engine to run up 7000, maybe even 11,000rpm, when the max hp/torque is around half of that? wouldn't all that revving beyond that point be, um, pointless?

Hmmm. I always thought that maximum torque may be at a lower rpm while maximum hp could be at the higher rpm's. I'm a bit too tired to concentrate. But it goes back to the formula:

hp= (torque x rpm)/5252.

That's why some cars like the Corolla XRS needs to be literally abused to get its highest performance numbers.......

[badkuk]

pero, say your car's max hp is at 6000rpm. what's the use of designing the engine such that it revs up to 7000rpm? why not put some kind of limiter at 6000rpm, since revving any higher really doesn't do any good?

[ghosthunter]

pero, say your car's max hp is at 6000rpm. what's the use of designing the engine such that it revs up to 7000rpm? why not put some kind of limiter at 6000rpm, since revving any higher really doesn't do any good?

Assuming:
Your max HP is at 6000rpm
your max torque is at 4000rpm
your drop in RPM when shifting is 3000 rpm
so your ideal shift rpm will be 7000 rpm to maximize accelation.

[skylineGTR]

hmmm.. hindi ba mas maganda talaga pag high reving ung engine para pagnakuha mo ung max hp ng lets say 6,800 rpm kunyari and redline is 8,000 rpm, edi meron ka pang 1,200 rpm na ur running at max hp like in the skyline GTR, unlike sa mga b16b engines kunyari na max hp ka at 8,200 rpm at nasa redline ka na agad so palit ka na ulit ng gear. well this is only my opinion

[badkuk]

oooohhhh....gets ko na po B)

[niky]

Besides the shifting point angle, engine rpms aren't limited by where maximum power occurs, but as to how much the engine can take.

That's why some engines have power curves that peak very close to the limiter, because even if they could make more power at higher rpms, if you push them just a bit more, they won't survive.

Other engines peak in power way before the limiter, but since they can survive revving past that peak, the manufacturer allows them to rev that high anyway.

[GerardTagayty]

hey guys... ive been looking for a thread to post my question but i didnt want to create a thread na for it.. this is the closest i guess... just a simple naive question...

i just realized na walang redline the car that i drive most of the time... i just realized this last night as i pulled out of a gas station along macapagal last night... i stepped on the gas too fast i guess to avoid the oncoming car (which was honestly still far) and para maabutan ko yan green light...

so my tires sorta squeelezed and i slid for more than 30 seconds i guess then i looked down on my rpm thingie... it was close to 6k then i realized wala akong redline... i was sorta scared i might destroy the engine or something...

by the way the car i drive is a jumbo suv... guzzles on gas... is that possible? walang redline? i found it weird lang... coz the rest of our cars may redline naman...

[EssB]

shifting on higher revs will maximize your gear ratio - meaning as you shift to the next gear, nasa peak pa rin yung torque mo as the rev drops => giving you the optimum acceleration.

[ghosthunter]

hey guys... ive been looking for a thread to post my question but i didnt want to create a thread na for it.. this is the closest i guess... just a simple naive question...

i just realized na walang redline the car that i drive most of the time... i just realized this last night as i pulled out of a gas station along macapagal last night... i stepped on the gas too fast i guess to avoid the oncoming car (which was honestly still far) and para maabutan ko yan green light...

so my tires sorta squeelezed and i slid for more than 30 seconds i guess then i looked down on my rpm thingie... it was close to 6k then i realized wala akong redline... i was sorta scared i might destroy the engine or something...

by the way the car i drive is a jumbo suv... guzzles on gas... is that possible? walang redline? i found it weird lang... coz the rest of our cars may redline naman...

if your engine is an EFI type, chances are it has a redline limiter. You just haven't reached the trigger RPM of the limiter.

[GerardTagayty]

wala po talaga.. wala man lang redline marker?

[Jayo]

wala po talaga.. wala man lang redline marker?

Your SUV does not have a "redline marker", same with my truck but they supposedly have engine rev and vehicle speed limiters programmed in their ecu's. This is supposedly set at the factory so that if your suv is stock you cannot over-rev your engine or get past the vehicle's set maximum speed.

What your guzzler? Try doing as search for rev limiter for your suv>

[GerardTagayty]

Your SUV does not have a "redline marker", same with my truck but they supposedly have engine rev and vehicle speed limiters programmed in their ecu's. This is supposedly set at the factory so that if your suv is stock you cannot over-rev your engine or get past the vehicle's set maximum speed.

What your guzzler? Try doing as search for rev limiter for your suv>

chevrolet suburban... i found it weird lang kase the rest of the cars i see meron marker... so yun...

heres a pic of the thingie... rev counter?

[niky]

chevrolet suburban... i found it weird lang kase the rest of the cars i see meron marker... so yun...

heres a pic of the thingie... rev counter?

The rev counter is on the left.

The redline is probably exactly at 6000 rpm. You haven't hit the rev limiter yet, most likely.

[mbt]

there are two ways of squeezing more power out of a piston engine: a) increasing displacement; b) increasing revs. Both result in cramming more fuel and air into the cylinder over a given period of time (i.e., a 4-liter engine revving at 1 rpm = a 2.0-liter engine at 2 rpm).

a large-displacement engine will usually have a low redline because of all that mass, but will produce gonzo torque at low rpm. it will also consume gonzo amounts of fuel in general. on the other hand, a low-displacement engine designed to rev to make power offers the "best of both worlds" in a sense, in that it will be capable of making good power if you want it to by revving it high and running it at high rpm... while it will sip fuel like any small-displacement engine if you keep the rpm low (although it will be slow and gutless at low rpm, relatively)

In a nutshell, not all engines have power and torque peaks at 5000-6000 rpm. Some high-revving engines like certain Honda and Toyota engines that are 2.0 liters or lower make their peak power beyond 7,000 rpm.

Between a large-displacement torquer and a small-displacement screamer though, i'll take the torquer. It will be much more comfortable and effortless to drive fast.

[mbeige]

Gas engines that rev high to get optimum power (HP) need the high RPM because when you're at speed, and the gearing matches high RPM, then you get the most at that speed to optimize performance and supposedly "win".

The only reason to put power at low RPM is when you're in a drag race when you're stopped and reach max speed from a standstill.

On a diesel, however, you need to know where the maximum torque is kasi that's where the advantage is. Diesel engines get the most torque at low RPM because the diesel combustion cycle is slower, and diesel fuel cannot combust faster than gasoline, hence the powerband at lower RPM. When you have a high revving diesel, smoke results in unburnt fuel.

Gas engines do not usually have high torque kaya they need to maximize their power to compensate for that, and usually this comes at a higher engine speed.